1. Field of the Invention
The present invention relates to a process for regenerating a catalyst of the type used in hydrocarbon conversion processes. More particularly, this invention relates to a process for regenerating a catalyst comprising fluorosulfuric acid, at least a portion of said catalyst having become deactivated due to the formation of stable catalytically inert species during contact with a hydrocarbon feedstock in an alkylation process.
2. Description of the Prior Art
It is well known in the prior art that as the alkylation reaction proceeds, an organic material will form and will accumulate in the fluorosulfuric acid catalyst phase. The material has been given a variety of names including red oil, sludge, organic sludge, acid oil and the like. This organic material is a natural by-product of acid-catalyzed hydrocarbon reactions such as occur during alkylation and has been described in the literature as a conjunct polymer (see Miron, S. and Lee, R. J., "Molecular Structure of Conjugated Polymers," J. Chem. Eng. Data, Vol. 8, p. 150-160 (1963), the disclosures of which are incorporated herein by reference). These conjunct polymers are complex mixtures of olefinic, conjugated cyclic hydrocarbons that may be formed from any type of hydrocarbon except aromatics. More specifically, they are believed to be cyclic polyolefinic hydrocarbons with a high proportion of conjugated double bonds, no two of which are in the same ring. Five membered ring systems predominate, but larger, and possibily also smaller, rings are believed to be present. The accumulation of this material will ultimately cause the activity of fluorosulfuric acid catalysts to decline until said catalysts cease to exhibit economic activity. In such cases, depending upon economic factors, the catalyst may be replaced or regenerated to restore desired activity levels.
One method for regenerating catalysts comprising fluorosulfuric acid has been suggested in U.S. Pat. No. 3,766,293, the disclosures of which are incorporated herein by reference. According to this metal, an alkylation catalyst comprising fluorosulfuric acid, at least a portion of which has become deactivated, may be regenerated by (1) contacting said catalyst with water so as to convert at least a portion of the fluorosulfuric acid to hydrogen fluoride and sulfuric acid; (2) removing at least a portion of the hydrogen fluoride from said catalyst by contacting the same with a paraffin so as to form a hydrocarbon phase containing hydrogen fluoride; and (3) treating said hydrocarbon phase with sulfur trioxide to regenerate the fluorosulfuric acid. However, since sulfur trioxide is a fairly expensive reagent, it would be desirable to have available a simple and convenient method for minimizing the consumption of sulfur trioxide in step (3) of U.S. Pat. No. 3,766,293.